3 syllables: Ra, di, us. Stress on Ra.
RAY-dee-uhs
/ˈɹeɪdiəs/
Radius is pronounced RAY-dee-uhs (/ˈɹeɪdiəs/). It has three syllables (Ra-di-us), with the stress on "Ra". Radius is a noun meaning a line segment from the center of a circle or sphere to any point on its circumference, or the corresponding distance. It also appears in anatomy as a forearm bone. The term encompasses geometric, mathematical, and anatomical senses, and is used in contexts ranging from geometry proofs to medical descriptions.
nounRadius is a noun meaning a line segment from the center of a circle or sphere to any point on its circumference, or the corresponding distance. It also appears in anatomy as a forearm bone. The term encompasses geometric, mathematical, and anatomical senses, and is used in contexts ranging from geometry proofs to medical descriptions.
"The radius of a circle is half its diameter."
"In anatomy, the radius is one of the two forearm bones."
"The engineer measured the radius to ensure a perfect arc."
Pronounce it as /ˈreɪ.di.əs/. The first syllable carries primary stress. Make a clear initial /reɪ/ with a long A, then a light /di/ and a soft, quick /əs/ ending. In careful speech, you’ll hear all three syllables: RA-di-us. You can listen to examples on Pronounce or language-dictionary audio clips to model the three-beat cadence.
Common errors: 1) Dropping the final -us to /ˈreɪ.di/ or saying /ˈræ.di.əs/ with wrong vowel in the first syllable. Correction: hold the long /eɪ/ in the first syllable and pronounce the final /əs/ clearly. 2) Misplacing stress as on the second syllable, producing /ˌreɪ.diˈəs/. Correction: keep primary stress on the first syllable /ˈreɪ.di.əs/. 3) Merging /di/ into /d/ with a reduced /ɪ/; aim for ⟨di⟩ as a distinct syllable. Practice: say RA-di-us, emphasizing the initial beat.
US/UK/AU share /ˈreɪ.di.əs/, but rhythm and vowel length can vary. US tends to be slightly more clipped in /ˈreɪ.di.əs/, with a faster final -əs. UK often preserves a crisper /ˈreɪ.di.əs/ with more precise vowel onset and a marginally longer /iː/ quality? in unstressed syllables, and AU mirrors US in rhotic delivery but may flatten the /ə/ to a schwa in casual speech. All maintain the three-syllable structure though tempo differs.
Because it interplays a stressed open syllable (RA) with a mid lax second syllable (di) and a reduced final syllable (əs). The mid /ɪ/ can distort to /i/ or /ɪ/ depending on speaker, and the final /əs/ often reduces to /əs/ or /s/ in rapid speech. Mastery requires keeping three distinct vowels and ensuring the /r/ or /ɹ/ onset in US/UK/AU, along with proper lip-tension for the /eɪ/ diphthong. Practice will stabilize the rhythm and prevent dropping the final syllable.
Think RA-di-us with explicit articulation of the diphthong /eɪ/ in the first syllable and a clear, unvoiced final /əs/. Emphasize the three-syllable pattern in audio content and include IPA markers near examples. For search intent, pair phrases like “radius pronunciation” with “how to say radius” and include audio cues: /ˈreɪ.di.əs/. This precise, searchable format improves match for voice queries and transcription accuracy.
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- US: rhotic /ɹ/ is prominent; keep the r-colored /ɹ/ at the onset. The first vowel /eɪ/ should be a clear diphthong, ending with a crisp /i/ before /əs/. - UK: non-rhotic; the /r/ is not pronounced unless followed by a vowel; ensure /ˈreɪ.di.əs/ with a lighter /ɜː/ quality on /ə/. Final /ə/ often realized as a schwa; maintain three distinct vowels. - AU: similar to US in rhoticity; ensure a relaxed jaw and slightly higher vowel time on /eɪ/; keep /əs/ crisp, avoiding extra vowel insertion. Use IPA references: /ˈreɪ.di.əs/.
Radius comes from Latin radius meaning an axle, ray, spoke of a wheel, or staff. In Medieval Latin, radius generalized to a ray or beam, which influenced its mathematical usage as a line from the center to the edge. In Renaissance geometrical texts, radius became standard terminology for the distance from circle center to the circumference. The earliest English attestations appear around the 15th–16th centuries in mathematical manuscripts, with later adoption into anatomy and physics as formal vocabulary. The word’s core sense—an emanating line or distance from a central point—remained stable, with specialized applications in different sciences. The metaphorical extension to “radius of influence” reflects the same radiating concept and has entered common usage in social sciences and policy analysis.
💡 Etymology tip: Understanding word origins can help you remember pronunciation patterns and recognize related words in the same language family.
Help others use "Radius" correctly by contributing grammar tips, common mistakes, and context guidance.
💡 These words have similar meanings to "Radius" and can often be used interchangeably.
🔄 These words have opposite meanings to "Radius" and show contrast in usage.
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Words that rhyme with "Radius"
Practice with these rhyming pairs to improve your pronunciation consistency:
🎵 Rhyme tip: Practicing with rhyming words helps you master similar sound patterns and improves your overall pronunciation accuracy.
